This project deals with gangliosides and their interactions with cations. Gangliosides are the most complex sphingolipids, containing at least one sialic acid and a ceramide attached to a glucose/galactose core. The structures of gangliosides vary in the number and type of carbohydrate residues and their substituents and in the length and degree of unsaturation and hydroxylation of both the long-chain base and fatty acyl moiety. Complexation of gangliosides with metal ions is considered to be of significant importance in a number of biochemical processes. However, the analytical techniques traditionally employed to study gangliosides are not able to provide detailed structural information about these complexes. The studies have been designed to determine: (1) the relative efficiency of formation of complexes between gangliosides and different cations in the gas phase; (2) localization of the cations in the complexes; (3) determination of relative affinities of different cations for specific portions of the gangliosides; and (4) the ability of cationization to provide structural information for unknown gangliosides.